Sway of Illusion

Any number of target creatures become the color of your choice until end of turn.
Draw a card.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.

Heartstone

Activated abilities of creatures cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Shifting Sky

As Shifting Sky enters, choose a color.
All nonland permanents are the chosen color.

Jaded Response

Counter target spell if it shares a color with a creature you control.

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Well-Laid Plans

Prevent all damage that would be dealt to a creature by another creature if they share a color.

Arcane Lighthouse

{T}: Add {C}.
{1}, {T}: Until end of turn, creatures your opponents control lose hexproof and shroud and can't have hexproof or shroud.

Tidal Visionary

{T}: Target creature becomes the color of your choice until end of turn.

Omen Hawker

{T}: Add {C}{U}. Spend this mana only to activate abilities.

Quickchange

Target creature becomes the color or colors of your choice until end of turn.
Draw a card.

Harbinger of the Seas

Douse

Island

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Distorting Lens

{T}: Target permanent becomes the color of your choice until end of turn.

Willbreaker

Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.

Alter Reality

Change the text of target spell or permanent by replacing all instances of one color word with another. (This effect lasts indefinitely.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Hibernation

Return all green permanents to their owners' hands.

King Crab

{1}{U}, {T}: Put target green creature on top of its owner's library.

Dismiss into Dream

Each creature your opponents control is an Illusion in addition to its other types and has "When this creature becomes the target of a spell or ability, sacrifice it."

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Myriad Landscape

Myriad Landscape enters tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Scuttlemutt

{T}: Add one mana of any color.
{T}: Target creature becomes the color or colors of your choice until end of turn.

Flashfreeze

Tidebinder Mage

When Tidebinder Mage enters, tap target red or green creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Tidebinder Mage.

Blind Seer

{1}{U}: Target spell or permanent becomes the color of your choice until end of turn.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Detection Tower

{T}: Add {C}.
{1}, {T}: Until end of turn, your opponents and creatures your opponents control with hexproof can be the targets of spells and abilities you control as though they didn't have hexproof.